Efficiency of nickel-aluminum catalysts by water washing

ABSTRACT

The method of increasing the efficiency for the conversion of 2butyne-1,4-diol to saturated products of a granular, foraminous catalyst which has been activated by removing about 5-30 percent of the aluminum from a nickel-aluminum alloy containing about 3560 percent by weight of nickel and about 40-65 percent by weight of aluminum after such efficiency has been reduced through extended use as a fixed-bed catalyst in the continuous hydrogenation of an aqueous mixture containing about 20-70 percent by weight of 2-butyne-1,4,-diol and about 30-80 percent by weight of water at a temperature of about 60*-150* C. under a hydrogen pressure of 2,500-5,500 psi. and a superficial gas velocity of at least about 0.5 foot per minute which comprises washing the catalyst with a wash medium consisting essentially of water in combination with a pressure which is less than the reaction pressure, the volume of said wash medium being at least about 50 percent of the volume of the catalyst bed.

United States Patent Frank et al.

[54] EFFICIENCY OF NICKEL-ALUMINUM CATALYSTS BY WATER WASHING [72]Inventors: Herman J. Frank, Seabrook; Irving Mocb, Jr., Harris County,both of Tex.

[73] Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

[22] Filed: Feb. 12 1969 21 Appl. 110.; 798,766

[52] US. Cl ..252/420, 252/411 R, 252/466 Q,

260/635 M, 260/635 Y, 260/642 [51] 1m. 01 ..Blj 11/02, B01 j 11/30 [58]Field of Search ..252/420, 412, 477 Q;

[56] References Cited UNITED STATES PATENTS 2,174,651 10/1939 Byrkit..260/631 H 2,222,302 11/1940 Schmidt et a1. ..260/635 M 2,232,6742/1941 Pyzel ..260/641 2,319,707 5/1943 Reppe et al. ..260/635 M2,604,455 7/1952 Reynolds et a]. ..252/412 2,863,928 12/1958 Indest..252/412 2,950,260 8/1960 Rosenbaum ..252/477 Q 2,967,893 1/1961 Hortet a1. ..260/635 M 3,154,589 10/1964 Moore ..260/635 Y 3,232,996 2/1966Graham et a1. ..260/635 Y 3,479,411 11/1969 Adam et al ..260/635 M1,915,473 6/1933 Raney ..252/477 Q 3,544,485 12/1970 Taira et al..252/477 Q 14 1 Sept. 12, 1972 FOREIGN PATENTS OR APPLICATIONS 508,9446/1939 Great Britain ..260/635 M 647,363 12/1950 Great Britain ..260/632HF 698,019 10/1953 Great Britain ..260/635 M 833,592 4/1960 GreatBritain ..252/412 Primary Examiner-Daniel E. Wyman Assistant Examiner-P.E. Konopka Attorney-Robert E. Partridge [5 7] ABSTRACT The method ofincreasing the efliciency for the conversion of 2-butyne-1,4-diol tosaturated products of a granular, foraminous catalyst which has beenactivated by removing about 5-30 percent of the aluminum from anickel-aluminum alloy containing about -60 percent by weight of nickeland about -65 percent by weight of aluminum after such efficiency hasbeen reduced through extended use as a fixed-bed catalyst in thecontinuous hydrogenation of an aqueous mixture containing about 20-70percent by weight least about percent of the volume of the catalyst bed.

5 Claims, No Drawings EFFICIENCY OF NICKEL-ALUMINUM CATALYSTS BY WATERWASHING BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention relates to the production of 1,4-butanediol, hereinafterreferred to as butanediol, by the hydrogenation of 2-butyne-l,4-diol,hereinafter referred to as butynediol.

2. Description of the Prior Art In U. S. application Ser. No. 795,722,filed Jan. 31, 1969, now abandoned an improved process for thehydrogenation of aqueous butynediol to butanediol is described. Thisprocess involves the hydrogenation of an aqueous mixture consistingessentially of about 20-70 percent by weight of butynediol and about30-80 percent by weight of water at a temperature of about 60-150C.under a hydrogen pressure of about 2,500-5,500 psi. and a superficialgas velocity of at least about 0.5 foot per minute in the presence of afixed-bed of granular, foraminous, nickel-aluminum catalyst which hasbeen activated by removing about 5-30 percent of the aluminum from anickel-aluminum alloy consisting essentially of about 35-60 percent byweight of nickel and about 40-65 percent by weight of aluminum.

The hydrogenation process should becarried out so as to convertbutynediol to saturated products as completely as possible withinpractical limits. One of the primary uses for butanediol is in theproduction of tetrahydrofuran by dehydration as described in U.S. Pat.No. 2,251,835 and German Pat. No. 1,043,342. The presence ofintermediate 2- butene-l,4-diol, hereinafter referred to as butenediol,in the hydrogenation product results in the formation of2,5-dihydrofuran, hereinafter referred to as dihydrofuran, anundesirable impurity in the dehydration product. It is particularlydesirable, therefore, that the amount of butenediol in the product bereduced to substantially zero during the hydrogenation.

When substantially fresh catalyst is being used in the hydrogenation, atemperature on the low side of the 60-150 C. range should be used, andthe butene diol occurs a major portion of the original efficiency of thecatalyst can be restored by increasing the reaction temperatureslightly, for example l-5C., thereby significantly reducing thebutenediol content of the product. After another extended period ofoperation, the butenediol content will again approach the tolerablemaximum and the temperature can again be raised with a similar result.This stepwise raising of the temperature in response to the build-up ofbutenediol in the product can be continued until an exit temperature ofabout 150C. is reached. At this point no further significant benefitsare obtained by incrementally raising the temperature and the catalystmust be replaced with fresh catalyst if the product is to stay withinspecifications.

SUMMARY OF THE INVENTION It has now been discovered that the efficiencyfor the conversion of butynediol to saturated products of a granular,foraminous catalyst which has been activated by removing about 5-30percent of the aluminum from a nickel-aluminum alloy consistingessentially of about 35-60 percent by weight of nickel and about 40-65percent by weight of aluminum can be increased after such efiiciency hasbeen reduced through extended use as a fixed-bed catalyst in thecontinuous hydrogenation of an aqueous mixture consisting essentially ofabout 20-70 percent by weight of butynediol and about 30-80 percent byweight of water at a temperature of about 60-l 50C. under a hydrogenpartial pressure of about 2,500-5,500 psi. and a superficial gasvelocity of at least about 0.5 foot per minute, measured as the hydrogenleaves the catalyst bed, by the process which comprises washing thecatalyst with a wash medium consisting essentially of water, the volumeof said wash medium being at least about 50 percent of the volume of thecatalyst bed. Preferably the water washing is carried out in combinationwith a reduction in pressure to a pressure which is not more than aboutpercent of the reaction pressure, and the volume of the wash medium isat least equal to the volume of the catalyst bed. It is quite surprisingthat this simple expedient of water washing effects a substantialimprovement in the efficiency of the catalyst.

DETAILED DESCRIPTION OF THE INVENTION The method of this inventionrelates to a process which uses as its starting material an aqueousmixture consisting essentially of about 20-70 percent by weight ofbutynediol and about 30-80 percent by weight of water. The termconsisting essentially of, as used throughout the specification andclaims, is meant to exclude only those unspecified ingredients orimpurities which prevent the results of the invention from beingrealized. These aqueous mixtures are readily obtained by the well knownreaction of acetylene and formaldehyde as described, for example, inU.S. Pat. Nos. 2,840,618; 2,871,273, 2,939,844 and 3,154,589. The amountof water and butynediol in the product will vary within the specifiedlimits, depending upon the concentration of the aqueous formaldehydeused in the reaction, and whether or not, and to what extent, theproduct is concentrated by distillation. Crude butynediol products areconventionally subjected to a thermal separation wherein formaldehyde,some water, and other volatile products are removed and recycled to thereaction.

Preferably the feed material to the hydrogenation reaction describedherein consists essentially of about 35-60 percent by weight ofbutynediol and about 40-65 percent by weight of water and mostpreferably about 50-60 percent butynediol and about 40-50 percent water.The preferred feeds often contain minor amounts of formaldehyde, butgenerally less than about 1 percent.

The hydrogenation process uses a fixed-bed of granular, foraminous,nickel-aluminum catalyst which has been activated by removing about 5-30percent of the aluminum from a nickel-aluminum alloy consistingessentially of about 35-60 percent by weight of nickel and about 40-65percent by weight of aluminum. Such catalysts are described in U.S. Pat.No. 2,950,260. These catalysts, unlike Raney nickel catalysts which havehad all of the aluminum removed from the nickelaluminum alloy, retainabout 70-95 percent of the aluminum contained in the original alloy.This residual aluminum acts as a support for the nickel and allows thecatalyst to retain the granular size characteristics of the originalalloy, whereby it is suitable for use in a fixed-bed process. Preferablythe nickel-aluminum alloy before activation consists essentially ofabout 40-45 percent by weight of nickel and about 55-60 percent byweight of aluminum.

Activation of the catalyst is generally carried out by treating thealloy with a dilute aqueous alkali solution which is fed at atemperature not in excess of 35C. whereby not more than about 1.5 molesof hydrogen are evolved for each mole of alkali consumed. Alkali metalhydroxides such as sodium, potassium and lithium hydroxides are suitablefor this use. Preferably the alkali is an aqueous solution containingabout 0.2 5-l percent by weight of sodium hydroxide and the exittemperature of the solution during activation does not exceed about 50C.It is preferable to remove about -30 percent of the aluminum originallycontained in the alloy since the resulting catalyst retains itsefficiency somewhat longer than catalysts activated by the removal ofless aluminum. When more than about 30 percent of the aluminum isremoved, the active layer of foraminous nickel may flake off and plugthe supporting screens of the catalyst bed or alternatively break upinto small particles which may be carried off in the hydrogenatedproduct.

The granular catalyst particles should have grain sizes in the range ofabout l-14 mesh. The term granular" is used herein to define catalystsconsisting essentially of particles having sizes falling within theselimits. Preferably the catalyst consists essentially of particles havinggrain sizes of about 2-10 mesh.

The hydrogenation reaction is generally carried out at a hydrogenpartial pressure of about 2,500-5,500 psi. and a superficial gasvelocity of at least about 0.5 foot per minute, measured as the hydrogenleaves the catalyst bed. With hydrogen pressures of less than about2,500 psi. uneconomically large amounts of catalyst are required, theamount of butene-diol contained in the product increases significantly,and the catalyst is quickly deactivated. Pressures above about 5,500psi. are not economical because they require special high pressureequipment. There is no upper limit on the gas velocity except thatimposed by the requirement that the catalyst be fixed bed rather thanfluidized. Preferably the hydrogen partial pressure is about 3,000-5,000psi. and the superficial gas velocity is at least about 0.8 foot perminute.

The reaction temperature may vary from about 60l50 C. When thetemperature is less than about 60C., uneconomically large amounts ofcatalyst are required to complete the reaction. Since the reaction isexothermic, the temperature measured at the reactor exit will besomewhat higher than at the reactor entrance. The temperature at thereactor exit should not exceed about 150C. At temperatures above about150C., by-product formation principally n-butanol, becomes excessive.Preferably the reaction temperature is maintained at about 70-l45C.

Since the hydrogenation reaction is exothermic it is necessary that heatbe removed. This is conventionally accomplished by recycling a majorportion of the reactor effluent back to the reactor with heat removalfrom the recycle stream. Preferably the recycle to fresh feed ratio isabout l040:l, that is, in the range of about 10:1 to about 40:1. Mostpreferably the recycle to fresh feed ratio is about 15-2521. Within thisrecycle range the temperature of the reactants fed to the reactor ispreferably maintained at about -125C. With a recycle to fresh feed ratioof about 20:1, the temperature of the reactants fed to the reactor canbe maintained constant by reducing the temperature of the recycle streamby about 23C.

Of course, the invention is not limited to a recycle process since othermethods of removing heat can be used. For example, the reaction could becarried out stepwise with heat removal between the steps. Inert diluentsor excess hydrogen could also be used to further remove the heat ofreaction.

The activated nickel-aluminum catalysts used herein are most active whenused under non-acidic conditions. Accordingly, it is preferred thatalkali be added to the reactants in sufficient amount to maintain a pHof about 6.5-8 at the reactor exit. The pH is specified at the reactorexit" because it has been observed that the pH sometimes varies betweenthe reactor feed point and the reactor exit. Control of the pH may beaccomplished by adding alkali to the fresh butynediol feed, by addingalkali to the reactor effluent being recycled, or both. Suitable alkalifor this use includes alkali metal hydroxides such as sodium, potassiumand lithium hydroxides, and the like. Most preferably the pH at thereactor exit is maintained at about 7-7.5.

The hydrogenation may be carried out in a single stage or the processmay involve two or more stages. In a preferred embodiment, butynediol ispassed to a primary hydrogenation stage employing recycle, and theproduct of this stage, containing some butenediol, is passed to asupplemental hydrogenation stage using the same type of catalyst andconditions, but without recycle, to form a final product which issubstantially free of butenediol. In this case it is necessary that thebutenediol content of the product of the first stage be reduced to avery low level. The butenediol content of the first stage product shouldbe maintained low enough that the temperature in the second stage can becontrolled during conversion of the remaining butenediol to butanediolwithout recycle being necessary.

In accordance with this invention the efficiency of the catalyst can beincreased after it has been reduced through extended use in thehydrogenation reaction by washing the catalyst with a wash mediumconsisting essentially of water. It is not necessary that the washmedium be pure water, but it should not contain any ingredients whichmaterially detract from the result which would be obtained with purewater. For example, the aqueous feed material or the aqueous productstream should not be used for water washing.

Preferably the water washing is carried out in combination with areduction in pressure to a pressure which is not more than about percentof the reaction pressure. Although a substantial improvement in catalystefficiency can be obtained by water washing at the reaction pressure,when the water washing is carried out in combination with a reduction inpressure parent difference in effectiveness.

considerably better results are obtained. In contrast, it has been foundthat reducing the pressure of the system to atmospheric without waterwashing has not significant effect upon the efficiency of the catalyst.

In order for the reduction in pressure to have any substantial effect itshould be carried out in combination with the water washing. By incombination with it is meant that the pressure reduction may be before,during, or after the water washing but, when it is before or after thewater washing, it should be sufficiently contemporaneous with the waterwashing that no substantial amount of reaction takes place in between.The extent of the improvement in catalyst efficiency will vary dependingupon the degree of reduction in pressure. For best results the pressureshould be reduced as far as practical. Preferably, the pressure isreduced to a pressure which is not more than about 50 percent of thereaction pressure and most preferably the reduced pressure is less thanabout 1,000 psi.

The volume of water passed through the catalyst bed should be at leastabout 50 percent of the volume of the catalyst bed for a significantresult. Preferably the volume of water used is at least equal to thevolume of the catalyst bed. Wash water volumes varying from l-l ,000times the volume of the catalyst bed have been used without anysubstantial difference in the effect on catalyst efficiency.

Other variables in the water washing procedure are not critical. Suchfactors as the rate of flow, temperature, duration, and the use ofrecycle or once-through utilization of the water do not appear to haveany substantial effect upon the results obtained. No difference inefficiency has been noted for wash water flow rates varying from 0.04 to2 gallons per minute per cu. ft. of

catalyst. The temperature of the water at the end of the water wash hasbeen varied from l30C. with no apparent difference in effectiveness.Wash times have also been varied from 3 .to 14 hours without any ap- Theactive life of the catalyst is maximized by using the catalyst at as lowa temperature as is practical for as long as is possible withoutexceeding the maximum limit for intermediate butenediol in the product.The water washing of this invention is more effective with a catalystwhose efficiency was reduced through use at a relatively low temperaturethan with a catalyst used at a higher temperature. Therefore, thepreferred procedure for extending the life of the catalyst is to usefresh catalyst at a low reaction temperature, for example 75C., until itno longer is producing a product having an acceptable butenediolcontent. The catalyst is then water washed with pressure reduction inaccordance with this invention. After water washing, the catalyst canagain be used at 75C. to produce specification product for anotherperiod of time. Alternate water washing and reuse at 75C. can becontinued until the degree of improvement in efficiency resulting fromwater washing has decreased to the point where it is no longereconomically practical. At this point the temperature of the reaction israised, for example to 76-801roc., with the result that specificationproduct is again produced. When the butenediol content of the productagain reaches the specification limit, another water wash may or may nothave a beneficial effect. When the effectiveness of water washingdiminishes to the point where it is no longer practical, raising thereaction temperature is the only means available for returning thebutenediol content of the product to specification.

The following examples, illustrating the novel process disclosed hereinfor improving the efficiency of a nickel-aluminum catalyst used in thehydrogenation of butynediol to butanediol, are given without anyintention that the invention be limited thereto. All parts andpercentages are by weight.

EXAMPLE 1 A stainless steel reactor having a diameter of 1.125 inchesand a 28-inch high catalyst bed (0.016 cu. ft.), used as a primaryhydrogenation stage, is charged with 778 grams of 4-8 mesh 0.l85-0.093inch) nickel-aluminum catalyst which has been activated by removal of 25percent of the aluminum from an alloy containing 42 percent nickel and58 percent aluminum. Activation of the catalyst is accomplished bypumping 0.5 percent aqueous sodium hydroxide down through the reactor ata flow rate of 2 gallons per minute per cubic foot of catalyst on aonce-through basis. The hydrogen evolved during the activation isremoved from the bottom of the reactor. The inlet temperature of thecaustic feed is 15C. and the exit temperature averages approximately16C. Activation is accomplished in 16.5 hours with an average aluminumremoval rate of 0.025 percent per minute. Caustic utility during theactivation averages 52 percent.

Fresh feed, prepared by reacting two moles of aq ueous formaldehyde withone mole of acetylene and containing 56 percent butynediol, 43 percentwater, and 1 percent high boilers, is fed to the reactor at the rate of34.2 lbs. of butynediol per cubic foot of catalyst per hour. The pH ofthe fresh feed is adjusted with caustic to about 7.3 measured at thereactor exit. Hydrogen is fed to the reactor at a hydrogen partialpressure of 3,800 psi. and a superficial gas velocity of 1 foot perminute, measured as the hydrogen leaves the catalyst bed. With therecycle to fresh feed ratio at 20: 1, there is a 22C. temperaturedifferential within the reactor and product is recovered at the rate of35.8 lbs. of butanediol per cu. ft. of catalyst per hour. The feedtemperature is initially at C.

During the run all operating conditions are held constant except for theinlet temperature which is increased periodically to maintain thebutenediol bleedthrough rate at a low level. Periodically duringthe runa sample of the product is analyzed to determine the butenediol content,measured as parts per million of dihydrofuran impurity, on the totalorganic basis, formed upon dehydration of the product totetrahydrofuran.

At various times during the run the reaction is shut down, that is,pumping of the feed through the reactor is stopped. During some of theseshutdowns either the reactor is depressurized, the catalyst is washedwith water, or both. The water washes are carried out with distilledwater at the rate of 0.1 gallon per minute per cu. ft. of catalyst at25C. for 4 hours on a once-through basis. Table 1 contains a tabulationof the shutdowns which involve depressurization, water washing, or bothincluding data taken before the shutdown and after equilibrium isestablished following the shutdown.

TABLE I Before shutdown During shutdown After shutdown Teniper-Diliydro- 'Ieinpor- Diliydro- Catalyst attire, iuran, Catalyst Pressure,Water Catalyst aturo, iuran, 1i1e,hr p.p.in. life, hr. p.s.i. \vaslilife, lir. C. p.p.ni.

174 75-97 10, 200 178 3, 800 Yes 194 75-97 7, 430 240 75-97 9, 216 244Yes 255 75-00 3, 720 310 75-96 7, 292 310 0 NO 322 70-118 10, 730 32276-98 10, 730 323 3, 800 Yes 325 75-116 5, ()0

EXAMPLE 2 formed upon dehydration of the product to tetrahydrofuran.

A stainless steel reactor having a 1.77-inch inside diameter and acatalyst bed 12 feet high (0.185 cu. ft. used as a primary hydrogenationstage, is charged with At various times during the run, the reaction isshut down. During some of these shutdowns either the reac- 22 lbs. of4-8 mesh (0.1850.093 inch) nickel-alutor is depressurized, the catalystis washed with water, minum catalyst which has been activated by the orboth. The water washes are carried outwith distilled removal of percentof the aluminum from an alloy water at the rate of 0.1 gallon per minuteper cubic foot containing 42 percent nickel and 58 percent aluminum. ofcatalyst at 25C. for 8 hours on a once-through basis. Activation of thecatalyst is accomplished by pumping Table 11 contains a tabulation ofthe shutdowns which 0.5 percent aqueous sodium hydroxide up through the20 involve either depressurization, water washing, or both reactor on aonce-through basis at a flow rate of 2 galincluding data taken beforeand after the shutdown.

TABLE 11 Before shutdown During shutdown After shutdownTornporl)iliy(lr0 'loinper- Dihydro- Catalyst utnro, i'uriin, Catalystlrossuro, Water Catalyst attire, furun, lilo, (J. 1i.p.in. l1l(.,ll1'.l).s.i. wash life, lir. p. i.n|.

75-07 1,831) 14 1,000 Yi 27 75-J7 J50 7m? em0 27 3,800 Y( s 37 75-07 56470-94 2, 400 81 o .10 754w 1, 860 70-118 s, 000 18!! 0 ins 7on7 a, 70071-100 4, 370 212 0 21s 7.5-01; 'i, (150 75-06 3, (350 21s 0 22s 76-5171, 825 76-98 10, 300 350 3, 800 357 7mm 7, 970 80-102 10,100 405 0 41580-102 0, 100

lons per minute per cubic foot of catalyst. Hydrogen EXAMPLE 3 evolvedduring the activation is removed from the top of the f i temperatur? ofthe caustic entering A stainless steel reactor having a 1.77-inch insidethe s Is 25 tfmperature averages diameter and a catalyst bed 12 feethigh (0.185 cu. ft), about 32 C. The activation is continued for a totalof 8 d h d t h r d hours with an average aluminum removal of 0.052peruse as a pnmary y rogena S age? IS 0 age wl (22 lbs. of 4-8 mesh*0.185-0.093 inch) nickel-alucent per minute. Caustic utility during theactivation averages 70 percent. Immediately after 25 percent of mmumCatalyst whlch has been. actwated by the the aluminum has been removed,the catalyst is water l' l of percent the alummum from washed withdistilled water for 8 hours at a flow rate of c0n tam mg 42 percentmckfzl and 58 Percent alummllm' 2 gallons per minute per cubic foot ofcatalyst. The pH Actwanon of the catalysi accompl lshed by pumpmg of theeffluent is when the water washing is 0.5 percent aqueous sodiumhydroxide down through Completed the reactor at a flow rate of gallonsper minute per Fresh f d prepared by reacting two moles f aque cubicfoot of catalyst on a once-through bas s. The tem- Ous f ld h d with onemoie f acetylene and com perature of the caustic entering the reactor 1825C. and mining 5 percent butynediol, 43 percent water' and i the exittemperature initially is about 45C. and drops percent high boilers, isfed to the reactor at the rate of to 35 the activation progresses- Theactivation is 342 lb f b di l per bi f f catalyst per continued for atotal of 1 hour and 23 minutes and the hour. The pH of the fresh feed isadjusted with caustic average Caustic utility is 95 P to about 7.3measured at the reactor exit. Hydrogen is fed to the reactor at asuperficial hydrogen velocity of Fresh feed prpared by reactmg 2 molesof 99 about 1 foot per minute measured as the hydrogen formaldehyde with1 mole of acetylene and containing leaves the catalyst bed, and at ahydrogen partial pres- 50-55 percent butynedlool and 45*50 parcelt Wateri sure of 3,800 psi. The recycle to fresh feed ratio is 20:1 to the{eactor 90 The PH of the fresh feed 15 and product is recovered at therate of 38.5 lbs. of buadjusted Caustic to about measured at thetanediol per cubic foot of catalyst per hour. The feed reactor exlt-Hydr0gen 1S fed to i reactor at a temperature is initially 75C. andthere is a 22C. temhydrogen Partial P165511re 3,800 P and a Superficialpe 'atu 'e differential within the reactor gas velocity Of 1 fOOt perminute, measured as the during the run all operating conditi s re h ldhydrogen leaves the catalyst bed. Initially the feed is stant except forthe inlet temperature which is in charged at the rate of 17.1 lbs. ofbutynediol per cubic creased periodically to maintain the butenediolbleedfoot of catalyst per hour. The recycle to fresh feed ratio throughrate at a low level. Periodically during the run is initially 20:1 thetemperature differential within the a sample of the product is analyzedto determine the butenediol content, measured as parts per million ofdihydrofuran impurity, on the total organic basis,

all

reactor is initially 22C., and product is recovered initially at therate of 17.9 lbs. of butanediol per cubic foot 17.1 catalyst per hour.

During the run all operating conditions are held constant except for thefeed rate, the recycle to fresh feed ratio and the rate at which productis recovered. As the fresh feed rate increases and the recycle ratiodecreases there is a resultant increase in temperature differentialwithin the reactor. Between the 20th and 32nd hours of operation thefresh feed rate is increased to 24.7 lbs. of butynediol per cu. ft. ofcatalyst per hour with a corresponding decrease in the recycle to freshfeed ratio so as to provide 25.8 lbs. of butanediol per cu. ft. ofcatalyst per day. Between the 32nd and 44th hours of operation the freshfeed rate is 19.9 lbs. per cu. ft. of catalyst per hour. Between the44th and 56th hours the fresh rate is again 17.1 lbs. of butynediol percu. ft. of catalyst per hour. After 56 hours the fresh feed rate isincreased to 19.9 lbs. of butynediol and then slowly decreased to 17.1lbs. of butynediol over the next 28 hours. The fresh feed rate remainsat 17.1 lbs. of butynediol per cu. ft. of catalyst per hour for theremainder of the run.

Periodically during the run a sample of the product is analyzed todetermine the butenediol content, measured as parts per million ofdihydrofuran. At various times during the run the reaction is shut down.During one of these shutdowns the reactor is depressurized. Duringanother shutdown the reactor is depressurized and the catalyst is washedwith well water containing 200 parts per million of calcium chloride for8 hours at 25C. at the rate of 0.1 gallon per minute per cubic foot ofcatalyst. The following data is obtained.

We claim 1. The method of increasing the efficiency of a granular,foraminous catalyst after such efficiency has been reduced throughextended use in producing 1,4- butanediol by the continuoushydrogenation of an aqueous mixture consisting essentially of 20-70percent by weight of 2-butyne-l ,4-diol and 30-80 percent by weight ofwater in the presence of a fixed bed of said granular, foraminouscatalyst, at a temperature of 60150 C. under a partial pressure of2,5005 .500 ps and a superficial gas velocity of at least 0.5 foot perminute, measured as the hydrogen leaves the catalyst bed, said granularforaminous catalyst being a nickelaluminum catalyst which has beenactivated by removing 5-30 percent of the aluminumfrom a nickel-aluminumalloy consisting essentially of -60 percent by weight of nickel and -65percent by weight of aluminum, said method of increasing such efficiencyconsisting essentially of washing said catalyst with water, the volumeof said wash water being at least 50 percent of the volume of thecatalyst bed, said washing being carried out in combination with areduction in pressure to a pressure which is not more than 90 percent ofthe reaction pressure.

2. The process of claim 1 in which the volume of the wash water is atleast equal to the volume of the catalyst bed.

3. The process of claim 2 in which the pressure is reducedduring waterwashing of the catalyst.

4. The process of claim 2 in which the reduced pressure used incombination with the water washing of the TABLE III Before shutdownDuring shutdown Alter shutdown Tompor- Dihydro- Temper Dihydro- Catalystattire, iuran, Catalyst Pressure, Water Catalyst ature, l'uran, life, hrC. ppm. life, hr. p.s.i. wash lilo, hr. p.p.m.

13 00-112 17 18 0 N0 2!) 00-112 110 77 00-112 550 82 0 YtS 88 210-112 6Although the invention has been described and exemplified by way ofspecific embodiments, it is not intended that it be limited thereto. Aswill be apparent to those skilled in the art, numerous modifications andvariations of these embodiments can be made without departing from thespirit of the invention or the scope of the following claims.

v 5 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,9- 93 Dated September 121i 1972 v Inventor(s) Hernan J. Frank and IrvingMoch Jr; i

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 5, line 63, "76- 804roc." should read Column 7, line 62, "during"should read "During",

' Column 8, line 38, "(22 lbs. of 4-8 mesh 0.l85-0.095 inch)" shouldread -22 lbs. of 4-8 mesh (o.185-o .o 93 inch) a Column 8, line 45, "ofgallons" should read I --of 2 gall ons--. a 5

Column 8, line 67, "foot 17.1 catalyst per a hour" should read -foot ofcatalyst per hour".

- Column 9, line 1 4-, "fresh rate" should read --fresh feed rate--.

Column 10, line 10, "2500-5500 ps" should read "2500-5500 psi--.

Signed and sealed this 13th day of August 1974.

(SEAL) Attest:

McCOY M-. GIBSON, JR. c. MARSHALL DANN Attesting Officer Commissioner ofPatents

2. The process of claim 1 in which the volume of the wash water is atleast equal to the volume of the catalyst bed.
 3. The process of claim 2in which the pressure is reduced during water washing of the catalyst.4. The process of claim 2 in which the reduced pressure used incombination with the water washing of the catalyst is not more than 50percent of the reaction pressure.
 5. The process of claim 4 in which thenickel-aluminum alloy consists essentially of 40-45 percent by weight ofnickel and 55-60 percent by weight of aluminum, the catalyst consistsessentially of particles having grain sizes of 2-10 mesh.